Rotted sheathing repair/replace

[Peashow]

We are currently selling our home, but we have received the following repair list items from the buyer's lender. The part in question is regarding the sheathing of the roof. It seems that the estimate they had quoted is extremely low, not even half of what we have been quoted for from contractors. Most are quoting us around $900. They are saying they will have to remove the roof to replace the sheathing. I was wondering if, firstly, are we reading this wrong and they want a simpler fix than we are getting quotes for. Secondly, is there a quicker or easier way to get this done? Not sure how thoroughly this inspector will check when he walks through again. The roof in question is a small part that overhangs a storage area, kind of like a shed and a crawl space.